Solubility Calculations of Methane and Ethane in Aqueous Electrolyte Solutions

Accurate calculation of light hydrocarbon solubilities in aqueous electrolyte solutions is critical for petroleum and geochemical applications. However, very few electrolyte Equations of State (e-EoS) have been used for calculation of light hydrocarbon solubilities. Thermodynamic calculation of gas (methane and ethane) solubilities in aqueous solutions of chloride salts are presented. This work introduces a new parameter estimation approach (which can predict well the liquid densities of aqueous solutions) for the electrolyte Cubic Plus Association EoS (e-CPA). The cation/anion-water interaction parameters are obtained from the regression of experimental mean ionic activity coefficients and liquid densities. The results show that the e-CPA with the new parameter estimation approach gives good agreements with the corresponding experimental data. The cation/anion-gas interaction parameters are obtained from the regression of experimental gas solubilities. The results show that the e-CPA with the new parameter estimation approach correlates the gas solubilities reasonably well. The gas dissolution mechanisms and salting effects are extensively analyzed and discussed for a deeper understanding of gas dissolution in aqueous electrolyte solutions.